This invention relates to recognition and more particularly to noise-dependent rejection decision.
Speech recognition is finding more uses today in noisy environments. Speech recognition involves matching acoustic models to input speech and generating probability scores for the match to the models. Simple score-difference-based decision has been reported by C. S. Ramalingam, Y. Gong, L. P. Netsch and Anderson in Proc. of IEEE Int. Conf. on Acoustics, Speech, and Signal Processing, entitled xe2x80x9cSpeaker-dependent Name Dialing in a Car Environment,xe2x80x9d Phoenix, March 1999. Speech recognition in these noisy environments such as use along a highway can cause severe problems in speech recognition.
In accordance with one embodiment of the present invention, improvement is provided by noise-dependent classification of the input that includes detecting noise level and providing a score value based on input recognition. A classifier is responsive to the detected input noise level and the score value for making acceptance or rejection decisions.
In accordance with another embodiment of the present invention, a speech recognition system includes a speech recognizer which has a database of in-vocabulary words that provides a difference score for an utterance relating to in-vocabulary words and a noise detector that detects noise level of the utterance and a classifier responsive to the detected noise level and the difference score for accepting or rejecting the closest in-vocabulary word as a recognized word.